How do I play melee carries?

Early on in lane, a Stout Shield can be a great way to reduce incoming damage on a melee carry. I know that wasn't directly your question, but I think it's worth pointing out since taking lane harass is one of the bigger difficulties melee heroes face.

Later on, you're certainly going to want to build some kind of big survivability item. In addition to Black King Bar, some typical options are:

• Heart of Tarrasque: gives lots of raw HP. Great on strength carries, but built by some agility carries too. Also gives massive health regen when not in combat.
• Assault Cuirass: gives armour and attack speed (also an aura with more armour/attack speed, and minus armour for enemies). Good when the enemy team mainly relies on physical damage.
• Manta Style: gives stats, move speed, and creates illusions of you which cause damage and create confusion (enemies don't know which of you to attack). Activating it can also be used to purge or evade some negative effects. Very popular on agility carries.
• Butterfly: gives huge amounts of agility/damage/attack speed, as well as 30% evasion from attacks. Very common on agility heroes.

What you build will depend on the hero, but most of the time you'll want to go for a mix of damage and survivability items.

Also as a general point, most carries don't want to be wandering into the middle of the fight right away - let someone else initiate, and then jump in once the fight has begun so you don't just get focused down. Don't let your farm go to your head and think you can 1v5 the other team, or even 1v2 for most of the game - all it takes is for someone to disable you and you'll get focused down before you can do any real damage.

A few tips:

• Abuse the advantages to being a melee hero, and definitely grab a Stout Shield/ Quelling Blade if you think you need one. Those items are fantastic at the start of the game.
• As a melee carry in the laning phase, if you are losing your lane, only stand close to your creep wave when going for a last hit, so you can avoid being harassed otherwise.
• In general the best way to increase your survivability is to build armor items on strength melees (as their natural str gain keeps their hp up), and to build strength/hp on agility melees.
• Build around your foes in every stage of the game. High harass lane? Grab a Stout Shield. Enemy lane is spamming a lot of spells? Grab a Magic Stick. Lots of crowd control getting you down? Grab a Black King Bar.

Most tips are usually specific to the heroes themselves though, so it's hard to tell you things for just "melee carries" as they can be very different. If you have any other questions, let me know. Good luck!